Article coated with aqueous dispersion of fluoropolymers in combination with epoxy-type film formers

ABSTRACT

Aqueous dispersions of fluorocarbon polymers in combination with the water-borne reaction product of (a) carboxyl-functional polymers, (b) polyepoxides and (c) tertiary amines are provided. Such dispersions can be applied to a variety of substrates by either conventional coating techniques or electrodeposition, and provide coatings that exhibit excellent release properties and high lubricity.

This is a division, of application Ser. No. 06/279,162, filed June 30,1981, now U.S. Pat. No. 4,335,030.

BACKGROUND OF THE INVENTION

There are many factors which militate in favor of aqueous dispersions.Among these are increased awareness of the environmental hazardsassociated with organic solvent vapors entering the atmosphere, thedesirability of a single system that can be applied not only by the moreconventional techniques of spray or roller coating but also byelectrodeposition, and the economy resulting from the substitution ofwater for some or all of the solvents in a coating composition.

Aqueous dispersions of perfluoroolefin polymers containing film-formingmaterials are known, as evidenced by U.S. Pat. No. 4,087,394 issued May2, 1978 to Concannon. The cured films obtained from such dispersionsoffer such advantages as excellent release properties, high lubricity,high resistance to heat and chemicals, and good electrical insulatingproperties.

The present invention, however, offers improvements by virtue of itsutilization of a unique water-borne film former based on the reactionproduct of a carboxyl-functional polymer, an epoxide, and a tertiaryamine.

This type of film-former is described in U.S. Pat. No. 4,247,439 issuedJan. 27, 1981 to Matthews and Sommerfeld.

SUMMARY OF THE INVENTION

According to the present invention there is provided an aqueousdispersion consisting essentially of:

(A) 90 to 10% by weight, based on the weight of (A) plus (B), of thereaction product of:

(1) at least 50%, based on the weight of (1) plus (2), preferably atleast 65%, most preferably about 78%, of an epoxy resin containing, onthe average, two terminal 1,2-epoxy groups per molecule and having anepoxy equivalent weight of 750-5000, preferably about 1500-4000, mostpreferably about 3000;

(2) a carboxy-functional vinyl polymer in an amount sufficient toprovide at least 2.50, preferably at least 3.50, equivalents of carboxylgroups, when the source of the carboxyl group is a monoprotic acid andat least 4.0 equivalents of carboxyl groups, when the source of suchgroups is a diprotic acid, per equivalent of 1,2-epoxy groups in theepoxy resin of (1), said polymer having a weight average molecularweight (determined by light scattering) of 10,000-50,000, preferably10,000-20,000, and an acid number of 200-500, preferably about 250-350,most preferably about 300;

(3) an aqueous solution of at least 1.50, preferably at least about2.50, equivalents of a tertiary amine per equivalent of 1,2-epoxy groupsin the epoxy resin of (1), said tertiary amine being selected from thegroup consisting of R,R₂ R₃ N, pyridine, N-methyl pyrrole, N-methylpiperidine, N-methyl pyrrolidine, N-methyl morpholine, and mixturesthereof and wherein R and R₂ are substituted or unsubstituted monovalentalkyl groups containing one or two carbon atoms in the alkyl portion andR₃ is a substituted or unsubstituted monovalent alkyl group containing1-4 carbon atoms; and

(4) 10-90% of the amount required for stoichiometric reaction with thecarboxyl-functional polymer of (2), of at least one primary, secondaryor tertiary amine or monofunctional quaternary ammonium hydroxide, suchthat the pH of the reaction product of (A) is greater than 8.5,preferably between 9 and 10;

Y being at least about 6+0.75 (2^(x)), where Y is the milliequivalent ofcarboxyl groups neutralized by primary, secondary or tertiary amines ormonofunctional quaternary ammonium hydroxice per 100 grams of acidpolymer plus epoxy, and X is the epoxy equivalent weight divided by1000; and

wherein for increasing ratios of carboxyl groups to 1,2-epoxy groups,the amount of amine is increased to keep the carboxyl-functional polymerwater dispersible;

(B) 10-90% by weight, based on the weight of (A) and (B), of afluorocarbon polymer which is preferably:

(1) a polymer of hydrocarbon monomer completely substituted withfluorine atoms or a combination of fluorine atoms and chlorine atoms;

(2) a perfluoroolefin copolymer of tetrafluoroethylene andhexafluoropropylene;

(3) a particulate copolymer containing

(a) 99.5-92% tetrafluoroethylene,

(b) 0.5-8%, preferably 3%, of at least one perfluorinated vinyl etherhaving the formula:

    CF.sub.2 ═CF--O--R.sub.f

in which R_(f) represents one or more perfluoroalkyl radicals havingfrom 1 to 10 atoms or a particulate perfluorinated ether having theformula: ##STR1## in which n is zero to four, and, optionally, (c)hexafluoropropylene; or

(4) polyvinyl fluoride; or

(5) polyvinyl difluoride; or

(6) a fluorocarbon telomer, having a number average molecular weight ofapproximately 25,000, obtained by telomerizing one mole oftetrafluoroethylene in the presence of a peroxide catalyst and 0.01 to0.6 moles of an active telogen, preferably methylcyclohexane; or

(7) an elastomeric copolymer comprised of 70% to 30% by weight ofpolyvinyl difluoride and 30% to 70% by weight of hexafluoropropene;

(c) optionally, up to 20% by weight, based on the weight of (A), of anaqueous nitrogen or phenolic crosslinking agent;

and, optionally, pigments, colorants, and stabilizers; wherein thedispersion comprises 5-50%, by weight of the dispersion, of (A) and (B),the remainder being water and an organic liquid or a mixture of organicliquids not exceeding the weight of the water in the dispersion.Additionally, articles coated or impregnated with these dispersions areprovided. (Percentages, proportions and ratios herein are by weightexcept where indicated otherwise.)

DETAILED DESCRIPTION OF THE INVENTION

The aqueous dispersion of this invention is capable of depositing, byroller or spray coating or by electrodeposition, a wet film which, uponbaking at between 100° C. and 370° C., provides a tough, continuouscoating of high lubricity, chemical and heat resistance, in addition toexcellent electrical insulating and release properties. A variety ofsubstrates, such as metal or ceramics, can be coated with the dispersionof this invention. Depending upon the end use anticipated, theproportion of fluoropolymer present in the invention will vary. If afluoropolymer-rich surface with enhanced release properties is desired,about 40-60% by weight, based on the combined weight of fluoropolymerand epoxy film-formers, of fluoropolymer is desirable. Alternatively, ifmere enhancement of lubricity is desired, about 20-40% by weight offluoropolymer is desirable.

The water-borne coating composition of the invention includes a solutionor dispersion of the reaction product of an epoxy resin, a tertiaryamine, and a carboxyl-function polymer. By mixing these components in arandom order and utilizing aqueous solutions of highly specific tertiaryamines such as dimethyl ethanol amine, the result is a stable,water-soluble or dispersible salt of a polymeric quaternary ammoniumhydroxide and a carboxyl-functional polymer. While this salt can becrosslinked without the addition of external crosslinking agents, theoptional addition of an external crosslinking agent, such as an aqueousphenolic or nitrogen resin, also affords a crosslinkable solution ordispersion which is stable at room temperature. Both compositions, thesalt and the solutions or dispersion containing an external crosslinkingagent, are infinitely dilutable with water.

Whether the coating composition is a solution or a dispersion is largelydependent on the nature of the particular amine used, the stoichiometryof the system, and the epoxy equivalent weight. Even when thecomposition is opaque some of the resinous components may be dissolved,and when the composition appears to be a clear solution it is possiblethat small amounts of the components are in a dispersed state. For sakeof simplicity, hereafter the term "dispersion" will be used to denotethe water-borne coating composition.

The dispersion, with or without an external crosslinking agent, asprepared, usually has a pH of above 7. Upon drying, a hard,solvent-resistant film having excellent resistance to acids, bases, hotwater, and detergent results. To obtain dispersion stability when mixedwith fluoropolymer, the epoxy/amine/polymeric acid dispersion shouldhave a minimum pH of 8.5, preferably between 9 and 10. This is becausethe fluoropolymer dispersions preferred for use in the invention aremore stable in a basic medium. As the epoxy/amine/polymeric acidreaction product is more acidic than the fluoropolymer dispersions, theacidity of the reaction product is first neutralized with amine or aquaternary ammonium hydroxide before the addition of the basicfluoropolymer dispersion. Otherwise, the pH of the fluoropolymerdispersion is changed, leading to a destabilization characterized by thefluoropolymer being "kicked out" of dispersion.

The low molecular weight epoxy resins to be utilized in the presentinvention are commonly known in the art. One class of such resins isbased on the condensation products of epichlorohydrin and bisphenol A.For a more detailed description of those epoxy resins that are eithersuitable or preferred for use in the invention, see U.S. Pat. No.4,247,439 issued Jan. 27, 1981 to Matthews and Sommerfeld (incorporatedin this description by reference).

The quantity of the epoxy resin to be utilized in the coatingcomposition of this invention is determined in relation to the amount ofcarboxyl-functional polymer and the relative amounts are dependent onthe end use application of the coating but there must be at least 50%,preferably in the range of 65-90%, of epoxy resin present. There mustbe, furthermore, at least 2.50, preferably at least 3.50 equivalents ofcarboxyl groups per equivalent of 1,2-epoxy groups in the epoxy resin.This minimum equivalent requirement is valid for thosecarboxyl-functional polymers which contain monoprotic acids derived fromalpha, beta-ethylenically unsaturated acid monomers such as acrylicacid, methacrylic acid, monoesters of alkanols having 1-8 carbon atomswith diacids, such as maleic acid, itaconic acid, fumaric acid,mesaconic acid, citraconic acid and the like, and mixtures thereof. Forthose carboxyl-functional polymers which contain diprotic acids derivedfrom diacids such as maleic acid, itaconic acid, fumaric acid, mesaconicacid, citraconic acid, and mixtures thereof, the minimum requirement is4.0 equivalents, preferably at least 5.0 equivalents, of carboxyl groupper 1,2-epoxy groups. Usually, no more than 10.0, and preferably no morethan 6.0, equivalents of carboxyl groups, per equivalent of 1,2-epoxygroups, will be present.

The carboxyl-functional polymers utilized in this invention are preparedby conventional free radical polymerization techniques from at least oneethylenically unsaturated monomer and at least one ethylenicallyunsaturated acid monomer. The choice of the alpha, beta-unsaturatedmonomer(s) is dictated by the intended end use of the coatingcomposition and is practically unlimited. A variety of acid monomers canbe used; their selection is dependent on the desired final polymerproperties.

This acid monomer can be an ethylenically unsaturated acid, monoproticor diprotic, anhydride or monoester of a dibasic acid, which iscopolymerizable with the other monomer(s) used to prepare the polymer.

The most preferred acid monomers are acrylic acid, methacrylic acid, anditaconic acid.

The acid number of the polymers suitable for this invention is 200-500,which corresponds to concentrations of about 10-77% of the acid monomersby weight of the polymer. The acid number is the number of milligrams ofpotassium hydroxide required to neutralize one gram of the polymer. Forpurposes of illustration, an acid number of 500 corresponds to 64% ofacrylic acid, 76.5% of methacrylic acid, 57.5% of itaconic acid, or51.5% of maleic or fumaric acid in the polymer. Preferred acid numbervalues are 250-350. While acid number values of less than 200 can besuitable for preparing stable compositions of the epoxy/amine/polymericacid, it unexpectedly appears that such low acid numbers pose stabilityproblems in the present invention, which of course provides for additionof a fluoropolymer dispersion to the epoxy-type film-former.

Vinyl aromatic monomers are commonly utilized to be copolymerized withthe acid monomers.

Illustrative of these monomers are styrene, alpha-methyl strene, vinyltoluene, and the like. The best polymers, in terms of final filmproperties, are those in which this type of monomer is styrene. Thevinyl aromatic monomers can be present from 0-80% of thecarboxyl-functional polymer, preferably from 40-80%, most preferablyfrom 40-70%, and specifically at concentrations of about 42, 53, and66%. For some purposes 10-45% may be preferred and, in someapplications, the polymer contains no such monomer.

Other suitable monomers are esters of acrylic acid, methacrylic acid ormixtures thereof with C₁ -C₁₆ alkanols. Preferred esters are the methyl,ethyl, propyl, n-butyl isobutyl, and 2-ethylhexyl esters of acrylic acidor methacrylic acid or mixtures of such esters. These esters can bepresent in concentrations of 0-97%, preferably 50-90% for automotivefinishes and coil coatings and, for can coatings and appliance finishes,preferably 0-50%.

The polymers utilized in the water-borne coating composition of thisinvention have a weight average molecular weight, as determined by lightscattering or, more conveniently, gel permeation chromatography, using apolystyrene standard, calibrated by light scattering methods, of about10,000-50,000. The preferred weight average molecular weight range is10,000-20,000. For some applications a 13,000-18,000 molecular weight ispreferred. Here again, there is a difference between what is suitablefor preparing the present invention and what is suitable for merelypreparing a stable epoxy-type film-former. While average molecularweights for the copolymer of an aqueous epoxy film-former of the typeused herein can exceed 50,000, it was unexpectedly discovered that thoseaqueous epoxy film-formers with such high molecular weight copolymersprovide unstable dispersions of the present invention.

In order to further enhance the stability of the dispersion of thepresent invention, it is also desirable that the epoxy film-former havea copolymer with a high degree of functional periodicity, that is, acopolymer in which monopolymerization has been minimized. This isachieved by adding the monomers to the reaction vessel such that themore sluggishly reacting monomers are introduced first. Which monomersthis may be will, of course, depend on the mix used, but in any case,will be easily ascertained by those skilled in the art.

During the preparation of the coating composition of this invention, anaqueous solution of a tertiary amine, specified below, is brought incontact with a solution of an epoxy resin in organic liquid(s) or with asolution of an epoxy resin and a carboxyl-functional polymer. A widevariety of organic liquids can be used to dissolve the epoxy resins andthe carboxyl-functional polymers. Among the most commonly used solventsare alcohols. Examples of those alcohols useful in preparing the presentinvention are disclosed in the Matthews and Sommerfeld patent.

While the exact mode of the reaction is not fully understood, it isbelieved that the tertiary amine first reacts with thecarboxyl-functional polymer to form the corresponding salt which, inturn, can dissociate to allow the amine to react with the 1,2-epoxygroups of the epoxy resin. It is also possible, however, that thetertiary amine reacts directly with the 1,2-epoxy groups. In eithercase, the resulting quaternary ammonium hydroxide can react with thecarboxyl-functional polymer to yield a polymeric quaternaryammonium-amine mixed salt of a polymeric acid.

While most tertiary amines react with epoxy resins to form quaternaryammonium hydroxides, the preparation of the water-borne coatingcomposition of this invention is carried out utilizing at least onetertiary amine selected from the group: R₁ R₂ R₃ N, N-methylpyrrolidine, N-methyl morpholine, pyridine, N-methyl pyrrole, N-methylpiperidine, and mixtures thereof, wherein R₁ and R₂ are substituted orunsubstituted monovalent alkyl groups containing one or two carbon atomsin the alkyl portion and R₃ is a substituted or unsubstituted monovalentalkyl group containing 1-4 carbon atoms. The Matthews and Sommerfeldpatent discloses some preferred examples of R₁ R₂ R₃ N. Most preferredare trimethyl amine or dimethyl ethanol amine.

The amount of tertiary amine needed in the preparation of thewater-borne coating composition of this invention is determined by twofactors. As a minimum, there is required at least 1.50 equivalents oftertiary amine per equivalent of 1,2-epoxy groups, preferably at least2.5 equivalents, for the formation of stable dispersion. As the ratio ofthe number of carboxyl groups in the carboxyl-functional polymer to thenumber of 1,2-epoxy groups in the epoxy resin increases, the amount ofamine is also increased to keep the carboxyl-functional polymer waterdispersible. This excess amine is believed to form a salt with some orall of the excess carboxyl groups of the polymer. The excess amine, overthe amount required for stoichiometric reaction with thecarboxyl-functional polymer, should be such that the pH of theepoxy-type film-former (before adding the fluoropolymer) is at least8.5, preferably between 9 and 10. The amine utilized in excess of the1.50 equivalents of the highly specific tertiary amine per equivalent of1,2-epoxy groups need not be the same as, nor does it necessarily haveto be selected from the group of, the highly specific tertiary amines.Any primary, secondary or tertiary amine or monofunctional quaternaryammonium hydroxide can be utilized in neutralizing carboxyl groups ofthe carboxyl-functional polymer which are not already neutralized.

This water-borne coating composition of the invention also includes afluorocarbon polymer, comprising 10-90% by weight of the dispersed phaseof the aqueous dispersion of this invention. This fluorocarbon polymercan be of a hydrocarbon monomer completely substituted with fluorineatoms or a combination of fluorine and chlorine atoms. Typically, thispolymer would be polytetrafluorethylene (PTFE). The PTFE polymers to beutilized in this invention are aqueous dispersions or dry polymers andare well known in the art. They are described in, for example, U.S. Pat.No. 2,230,654, issued Feb. 4, 1941 to R. J. Plunkett (incorporatedherein by reference).

When the fluorocarbon polymer used is a copolymer of tetrafluoroethylene(TFE) and hexafluoropropylene (HFP), the TFE/HFP monomer weight ratiocan be 5-95/95-5, preferably 50-95/50-5, and most preferably 93-95/7-5,84-88/16-12, or 75-80/25-20. Representative methods of preparing suchcopolymers, which are either aqueous dispersions or dry polymers, aredescribed in U.S. Pat. No. 2,946,763, issued Mar. 29, 1957 to M. I. Broand B. W. Sandt (incorporated herein by reference).

The TFE/HFP monomer weight ratio is related to the "non-stick"properties desired in the cured films obtained from a dispersion of theinvention. Those copolymers known as "low melt", that is, those having arelatively low glass transition temperature, result in a cured film inwhich the fluoropolymer is more concentrated at the film-air interface.This fluoropolymer-rich surface is characterized by enhanced "non-stick"properties. In contrast, the "high melt" copolymers are more uniformlydistributed throughout the cured film, rather than being concentrated atthe surface. Such a film may be desired where lubricity is important butthere is not a need for maximum "non-stick" qualities. This process offluoropolymer migration is discussed in more detail in U.S. Pat. No.4,087,394 issued May 2, 1978 to Concannon (incorporated herein byreference).

Another fluoropolymer suitable for use in the present invention is aparticulate copolymer of 92-99.5% tetrafluoroethylene (TFE) and 0.5-8%,preferably 3%, of a perfluorinated vinyl ether such as perfluoro(propylvinyl ether) (PPVE). A more detailed description of such copolymers(referred to as PFA) is available in U.S. Pat. No. 4,252,859 issued Feb.24, 1981 to Concannon and Vary (incorporated herein by reference).

Also suitable for use in the present invention are polyvinyl fluorideand polyvinyl difluoride, as well as fluorocarbon telomers orelastomeric fluoropolymers. Those particular fluorocarbon telomers(fluorotelomers) preferred are obtained by telomerizing one mole oftetrafluoroethylene in the presence of a peroxide catalyst and 0.01 to0.6 moles of an active telogen, preferably methylcyclohexane. Fordetails of such a reaction and the resulting telomer, see U.S. Pat. No.3,067,262 issued Dec. 4, 1962 to Brady (incorporated herein byreference). Those elastomeric fluoropolymers (fluoroelastomers)preferred are comprised of 70% to 30% by weight of polyvinyl difluorideand 30% to 70% by weight of hexafluoropropene. For a more detaileddescription of such a polymer, see Canadian Pat. No. 720,545 issued Oct.26, 1965 to Rexford.

The fluoropolymers used should have molecular weights in excess of about20,000 (weight average, determined by melt viscosity measurements), asmaterials below this level tend to be waxy and unsuitable for preparingaqueous dispersions. The fluoropolymers, as prepared in aqueous media,contain particles of 0.05-15 micron diameter and have an averageparticle size, when used as prepared in aqueous dispersions, near 0.2micron. The particle size is measured by electron microscopy and thediameter of a particle is taken to be the average dimension of thesubstantially spherical particles.

The present invention also encompasses the optional addition ofpigments, colorants and stabilizers. In adding pigments, however, it wasdiscovered that the stability of the dispersion dictates firstdispersing the pigment in the acrylic portion of the epoxy acrylic-typefilm-former, before pigment can be added to the invention.

The aqueous dispersion of this invention can be applied by a variety oftechniques and to a variety of substrates known in the industry. Roller,dip and spray coating, as well as electrodeposition, can be utilized.The details of electrodeposition are discussed in the Matthews andSommerfeld patent cited above.

Films obtained from the aqueous dispersions of this invention can bedried and baked in a wide temperature range, up to approximately 370° C.Advantageously, the coated substrates are prebaked at approximately 150°C. for 1-30 minutes followed by baking between 200° C. and 345° C. forperiods up to 30 minutes. Films so obtained from the dispersions cancontain substantially completely fused polymer or partially orcompletely particulate fluorocarbon polymer imbedded in the film-formingmaterial which forms a substantially continuous film.

The invention can be further understood by referring to the followingexamples in which parts and percentages are by weight.

Preparation of Modified Epoxy Resin Reaction Product (According toExample 3 of the Matthews and Sommerfeld patent)

(A) Into a suitably equipped kettle, inerted with nitrogen, are addedthe following parts by weight:

Monobutyl Ether of Ethylene Glycol: 91.567

Normal Butanol: 32.503

Ethyl Acrylate: 14.453

Tertiary Butyl Perbenzoate: 0.026

In a separate vessel, the following are added and mixed:

Ethyl Acrylate: 54.764

Methacrylic Acid: 122.060

Styrene: 72.919

Normal Butanol: 2.050

Tertiary Butyl Perbenzoate: 2.351

The reactor is heated to reflux and the monomer mixture is added evenlyto the refluxing reactor over a two-hour period. Then 7.932 parts ofmonobutyl ether of ethylene glycol are added as a rinse for monomer feedlines. Reflux is maintained for one hour, at which point 55.500 parts ofnormal butanol is added. Reflux temperatures are maintained for anadditional hour at which point the heat is turned off and 72.623 partsof normal butanol are added, followed by 82.312 parts of dimethylethanol amine and 246.940 parts of deionized water. The product is asolution of styrene/ethyl acrylate/methacrylic acid//27.6/26.2/46.2polymer at 30.8% solids in solvent, water, and amine. The acid number ofthe product is 300.

(B) Into a suitably equipped kettle, inerted with nitrogen, are addedthe following parts by weight:

Monobutyl Ether of Ethylene Glycol: 8.400

"Epon 829" epoxy resin (Shell Chemical Co.): 86.978

Bisphenol A: 46.835

The kettle charge is heated to 130°-140° C., heat removed and allowed toexotherm to 175°-200° C. After the exotherm is exhausted, heat isapplied and the reaction mass is maintained above 165° C. for two hoursafter peak exotherm. At this point, a sample can be removed fordetermination of completion of reaction. Theoretical epoxy equivalentweight is 3000. 6.655 parts of monobutyl ether of ethylene glycol and26.366 parts of normal butanol are added to dilute the reaction mass andcool it to 100° C.

121.131 parts of the neutralized acrylic polymer prepared in (A) areadded rapidly followed by 23.181 parts of deionized water. The mass isheated to reflux temperature and held for twenty-five minutes. Heat isturned off and 288.155 parts of deionized water, preheated to 70°-80°C., is added evenly over a one-hour period.

The resulting product contains about 77.8% epoxy resin and 22.2% acrylicresin, by weight, with an equivalent ratio of acid polymer/amine/epoxyof about 4.6/3.0/1,0. X is 3, and Y is 51.5.

EXAMPLE 1

The following ingredients are mixed at room temperature:

(A)

(1) Demineralized water, 3421.36 gms.;

(2) N,N-diethyl-2-aminoethanol, 7.20 gms.; and

(3) An aqueous dispersion of a TFE/HFP copolymer having a monomer weightratio of 75/25 (containing 60% solids), 1200.2 gms.

(B)

2571.40 gms. of the aqueous solution of the "modified epoxy resinreaction product" (prepared as described above) is then added to 2812.5gms. of the mixture of (A).

(C)

Finally, 250.0 gms. of Union Carbide BKUA-2260 (a phenolic,heat-reactive, cross-linkable, resole-type resin [bonding resin] in theform of an aqueous dispersion which is 48% solids) is added to themixture of (A) and (B).

The resulting dispersion can be sprayed on a metal substrate, such as analuminum sheet, in which case it would be cured by a 15-minute pre-bakeat approximately 175° C. followed by a 15-minute baking period atapproximately 345° C. The cured film adheres well and also exhibits goodrelease properties.

EXAMPLE 2

(A) The following ingredients are mixed at room temperature:

(1) Deionized water, 3421.36 gms.;

(2) N,N-diethyl-2-aminoethanol, 7.20 gms.; and

(3) An aqueous dispersion of a TFE/HFP copolymer having a monomer weightratio of 75/25 (containing 60% solids), 1200.02 gms.

(B) The 2571.40 gms. of the aqueous solution of the modified epoxy resinproduct (prepared as described above) are added to the mixture of (A).

The resulting dispersion can be dried and baked as in Example 1 toobtain similar results.

What is claimed is:
 1. An article coated with a cured coating of anaqueous coating composition having a dispersed phase which consistsessentially of:(A) 90 to 10% by weight, based on the weight of (A) plus(B), of the reaction product of:(1) at least 50%, based on the weight of(1) plus (2), of an epoxy resin containing, on the average, two terminal1,2-epoxy groups per molecule and having an epoxy equivalent weight of750-5000; (2) a carboxyl-functional polymer in an amount sufficient toprovide at least 2.50 equivalents of carboxyl groups, when the source ofthe carboxyl group is a mono-protic acid, and at least 4.0 equivalentsof carboxyl groups, when the source of such groups is a diprotic acid,per equivalent of 1,2-epoxy groups in the epoxy resin, said polymerhaving a weight average molecular weight (determined by lightscattering) of about 10,000-160,000 and an acid number of 200-500; (3)an aqueous solution of at least 1.50 equivalents of a tertiary amine perequivalent of 1,2-epoxy groups in the epoxy resin, said tertiary aminebeing selected from the group consisting of R₁ R₂ R₃ N, pyridine,N-methylpyrrole, N-methyl piperidine, N-methyl pyrrolidine, N-methylmorpholine, and mixtures thereof and wherein R₁ and R₂ are substitutedor unsubstituted monovalent alkyl groups containing one or two carbonatoms in the alkyl portion and R₃ is a substituted or unsubstitutedmonovalent alkyl group containing 1-4 carbon atoms; and (4) 10-90% ofthe amount required for stoichiometric reaction with thecarboxyl-functional polymer of (2), of at least one primary, secondaryor tertiary amine or monofunctional quaternary ammonium hydroxide, suchthat the pH of the reaction product of (A) is greater than 8.5;Y beingat least about 6+0.75 (2^(x)), where Y is the milliequivalent ofcarboxyl groups neutralized by primary, secondary or tertiary amine ormonofunctional quaternary ammonium hydroxide per 100 grams of acidpolymer plus epoxy, and X is the epoxy equivalent weight divided by1000; and wherein for increasing ratios of carboxyl groups to 1,2-epoxygroups, the amount of amine is increased to keep the carboxyl-functionalpolymer water dispersible; (B) 10-90% by weight, based on the weight of(A) plus (B), of a fluorocarbon polymer; and (C) optionally, up to 20%by weight, based on the weight of (A), of a nitrogen or phenoliccrosslinking agent.
 2. The coated article of claim 1 in which component(A) is such that (A) (1), (A) (2), (A) (3) and (A) (4) comprise about0.1-50% by weight of (A) and the remainder of (A) is comprised of theliquid carrier which is water and, optionally, organic liquid in avolume ratio of from 70:30 to all water.
 3. The coated article of claim2 wherein the carboxyl-functional polymer is present in an amountsufficient to provide at least 3.50 equivalents of carboxyl groups, whenthe source of the carboxyl group is a monoprotic acid, and at least 4.0equivalents of carboxyl groups, when the source of such groups is adiprotic acid, per equivalent of 1,2-epoxy groups in the epoxy resin. 4.The coated articles of claim 2 wherein said carboxyl-functional polymeris present in an amount sufficient to provide no more than 6.0equivalents of carboxyl groups per equivalent of 1,2-epoxy groups in theepoxy resin.
 5. The coated articles of claim 2 wherein said epoxy resinhas an epoxy equivalent weight of 1500-4000.
 6. The coated article ofclaim 2 wherein said carboxyl-functional polymer is a polymer of atleast one α,β-ethylenically unsaturated monomer and at least oneα,β-ethylenically unsaturated acid.
 7. The coated article of claim 6wherein said α,β-ethylenically unsaturated acid is selected from thegroup consisting of acrylic acid, methacrylic acid, and itaconic acid.8. The coated article of claim 6 wherein said carboxyl-functionalpolymer has an acid number of 200-250.
 9. The coated article of claim 6wherein said carboxyl-functional polymer has an acid number of 250-350.10. The coated article of claim 3 wherein said carboxyl-funtionalpolymer is present in an amount sufficient to provide 3.0-5.0equivalents of carboxyl groups per equivalent of 1,2-epoxy groups andsaid tertiary amine of (C) is present in the amount of 2.75-3.5equivalents per equivalent of 1,2-epoxy groups.
 11. The coated articleof claim 13 wherein said carboxyl-functional polymer has the compositionof styrene/alkyl (meth)acrylate/α,β-ethylenically unsaturatedacid//20-70/10-60/15-54.
 12. The coated article of claim 2 wherein thetertiary amine of (A) (3) R₁ R₂ R₃ N is selected from the groupconsisting of trimethyl amine, dimethyl ethanol amine, methyl diethanolamine, diethyl methyl amine, ethyl methyl ethanol amine, dimethyl benzylamine, dimethyl propyl amine, dimethyl ethyl amine, dimethyl3-hydroxy-1-propyl amine, dimethyl 2-hydroxy-1-propyl amine, dimethyl1-hydroxy-2-propyl amine, and mixtures thereof.
 13. The coated articleof claim 6 wherein the tertiary amine of (A) (3) is dimethyl ethanolamine.
 14. The coated article of claim 1 in which component (A) consistsessentially of liquid carrier and the reaction product of:(1) not lessthan 65% by weight, based on the weight of (1) plus (2), of an epoxyresin containing, on the average, two terminal 1,2-epoxy groups permolecule, and having an epoxy equivalent weight of about 1500-4000; (2)a carboxyl-functional polymer in an amount sufficient to provide atleast about 3.50 equivalents of carboxyl groups, when the source of thecarboxyl group is a mono-protic acid, and at least 4.0 equivalents ofcarboxyl groups, when the source of such groups is a diprotic acid, perequivalent of 1,2-epoxy groups in the epoxy resin, the polymer having aweight average molecular weight (determined by light scattering) ofabout 10,000-80,000 and an acid number of about 250-350; (3) an aqueoussolution of at least about 2.0 equivalents of 1,2-epoxy groups in theepoxy resin, the tertiary amine being selected from the group consistingof R₁ R₂ R₃ N, pyridine, N-methylpyrrole, N-methyl piperidine, N-methylpyrrolidine, N-methyl morpholine, and mixtures thereof and wherein R₁and R₂ are substituted or unsubstituted monovalent alkyl groupscontaining one or two carbon atoms in the alkyl portion and R₃ is asubstituted or unsubstituted monovalent alkyl group containing 1-4carbon atoms; and (4) 10-90% of the amount required for stoichiometricreaction with the carboxyl-functional polymer of (2), of at least oneprimary, secondary or tertiary amine or monofunctional quaternaryammonium hydroxide, such that the pH of the entire system after mixingis between 9 and 10; Y being at least about 6+0.75 (2^(x)) where Y isthe milliequivalent of carboxyl groups neutralized by primary, secondaryor tertiary amines or monofunctional quaternary ammonium hydroxide per100 grams of acid polymer plus epoxy, and X is the epoxy equivalentweight divided by 1000; and wherein for increasing ratios of carboxylgroups to 1,2-epoxy groups, the amount of amine is increased to keep thecarboxyl-functional polymer water dispersible.
 15. The coated article ofclaim 13 wherein the reaction product of component (A) includes:(1)about 78%, based on the weight of (1) plus (2), of an epoxy resincontaining, on the average, two terminal 1,2-epoxy groups per moleculeand having an epoxy equivalent weight of about 3000; (2) acarboxyl-functional polymer in an amount sufficient to provide at leastabout 4.6 equivalents of carboxyl groups, when the source of thecarboxyl group is a mono-protic acid, and at least 4.0 equivalents ofcarboxyl groups, when the source of such groups is a diprotic acid, perequivalent of 1,2-epoxy groups in the epoxy resin, said polymer having aweight average molecular weight (determined by light scattering) ofabout 13,000-18,000 and an acid number of about 300; and (3) an aqueoussolution of at least about 3.0 equivalents of a dimethyl amino ethanolper equivalent of 1,2-epoxy groups in the epoxy resin.
 16. The coatedarticle of claims 1, 14 or 15 in which the fluorocarbon polymer ispolytetrafluoroethylene having a weight average molecular weight,determined by melt viscosity measurements, in excess of 20,000 and itsparticles having a minimum average dimension of 0.05 micron and amaximum average dimention of 15 microns (as measured by electronmicroscopy).
 17. The coated article of claims 1, 6 or 14 or 15 in whichthe fluorocarbon polymer is a tetrafluoroethylene/hexafluoropropylenecopolymer in a comonomer weight ratio range of 5-95/95-5, having aweight average molecular weight, determined by melt viscositymeasurements, in excess of 20,000 and its particles having a minimumaverage dimension of 0.05 micron and a maximum average dimention of 15microns (as measured by electron microscopy).
 18. The coated article ofclaims 1, 6 or 14 or 15 in which the fluorocarbon polymer is atetrafluoroethylene/hexafluoropropylene copolymer in a comonomer weightratio range of 93-95/7-5, having a weight average molecular weight,determined by melt viscosity measurements, in excess of 20,000 and itsparticles having a minimum average dimension of 0.05 micron and amaximum average dimension of 15 microns (as measured by electronmicroscopy).
 19. The coated article of claims 1, 6 or 14 or 15 in whichthe fluorocarbon polymer is a tetrafluoroethylene/hexafluoropropylenecopolymer in a comonomer weight ratio of 84-88/16-12, having a weightaverage molecular weight, determined by melt viscosity measurements, inexcess of 20,000 and its particles having a minimum average dimension of0.05 micron and a maximum average dimention of 15 microns (as measuredby electron microscopy).
 20. The coated article of claims 1, 6 or 14 or15 in which the fluorocarbon polymer is atetrafluoroethylene/hexafluoropropylene copolymer is a comonomer weightratio range of 75-80/25-20, having a weight average molecular weight,determined by melt viscosity measurements, in excess of 20,000 and itsparticles having a minimum average dimension of 0.05 micron and amaximum average dimension of 15 microns (as measured by electronmicroscopy).
 21. The coated article of claims 1, 6 or 14 or 15 in whichthe fluorocarbon polymer is a particulate copolymer containing:(A)99.5-92% tetrafluoroethylene; (B) 0.5-8% of at least one perfluorinatedvinyl ether having the formula:

    CF.sub.2 ═CF--O--R.sub.f

in which R_(f) represents one or more perfluoroalkyl radicals havingfrom 1 to 10 atoms or a particulate perfluorinated ether having theformula: ##STR2## in which n is zero to four; and (C) optionally,hexafluoropropylene.
 22. The coated article of claim 20 in which theperfluorinated vinyl ether is perfluoro(propyl vinyl ether).
 23. Thecoated article of claim 22 in which the particulate copolymercontains:(A) 97% tetrafluoroethylene; and (B) 3% perfluoro(propyl vinylether).
 24. The coated article of claims 1, 6 or 14 or 15 in which thefluorocarbon polymer is polyvinyl fluoride having a weight averagemolecular weight in excess of 20,000 and its particles having a minimumaverage dimension of 0.05 micron and a maximum average dimension of 15microns (as measured by electron microscopy).
 25. The coated article ofclaims 1, 6 or 14 or 15 in which the fluorocarbon polymer is polyvinyldifluoride having a weight average molecular weight in excess of 20,000and its particles having a minimum average dimension of 0.05 micron anda maximum average dimension of 15 microns (as measured by electronmicroscopy).
 26. The coated article of claims 1, 6 or 14 or 15 in whichthe fluorocarbon polymer is a fluorotelomer obtained by telomerizing 1mole of tetrafluoroethylene in the presence of a peroxide catalyst and0.01 to 0.6 moles of methylcyclohexane, and having a weight averagemolecular weight in excess of 20,000 and its particles having a minimumaverage dimension of 0.05 micron and a maximum average dimension of 15microns (as measured by electron microscopy).
 27. The coated article ofclaims 1, 6 or 14 or 15 in which the fluorocarbon polymer is afluoroelastomer comprised of 70% to 30% by weight of polyvinyldifluoride and 30% to 70% by weight of hexafluoropropene, and having aweight average molecular weight in excess of 20,000 and its particleshaving a minimum average dimension of 0.05 micron and a maximum averagedimension of 15 microns (as measured by electron microscopy).
 28. Thecoated article of claims 1, 6 or 14 or 15 in which the fluorocarbonpolymer comprises 40-60%, by weight, of the dispersed phase.
 29. Thecoated article of claims 1, 6 or 14 or 15 in which the fluorocarbonpolymer comprises 50-55%, by weight, of the dispersed phase.
 30. Thecoated article of claims 1, 6 or 14 or 15 in which the fluorocarbonpolymer comprises 20-40%, by weight, of the dispersed phase.